Gearbox for a hybrid powertrain and method to control the gearbox

ABSTRACT

A gearbox that includes an input shaft ( 8 ) and an output shaft ( 20 ); a first epicyclic gear ( 10 ) that is connected to the input shaft ( 8 ); a second epicyclic gear ( 12 ) that is connected to the first epicyclic gear ( 10 ); a first electrical machine ( 14 ) that is connected to the first epicyclic gear ( 10 ); a second electrical machine ( 16 ) that is connected to the second epicyclic gear ( 12 ); a first gear pair ( 60 ) that is arranged between the first epicyclic gear ( 10 ) and the output shaft ( 20 ); and a second gear pair ( 66 ) that is arranged between the second epicyclic gear ( 12 ) and the output shaft ( 20 ). A side shaft ( 18 ) is arranged between one of the epicyclic gears ( 10, 12 ) and the output shaft ( 20 ) ( 18 ) and connected to the output shaft ( 20 ) through a final gear, ( 21 ) ( 21 ) which includes a gear element ( 92 ), that is arranged at the side shaft ( 18 ) in a disengagable manner. Also, disclosed is a method for controlling the gearbox. Also a vehicle ( 1 ) that includes such a gearbox ( 2 ), and a method to control such a gearbox ( 2 ). Also a computer program (P) to control a gearbox ( 2 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §371 national phase conversion ofPCT/SE2014/050335, filed Mar. 20, 2014, which claims priority to SwedishApplication No. 1350392-5, filed Mar. 27, 2013, the contents of whichare incorporated herein by reference.

BACKGROUND AND PRIOR ART

The present invention concerns a gearbox. The invention concerns also avehicle that comprises the gearbox, a method to control the gearbox, acomputer program to enable a computer to carry out the method to controlthe gearbox, and a computer program product comprising the program codeof the computer program stored in a computer-readable medium.

Hybrid vehicles can be driven by a primary engine, which may be acombustion engine, and a secondary engine, which may be an electricalmachine. The electrical machine is equipped with at least one energystore, such as an electrochemical energy store, for the storage ofelectrical energy, and regulating equipment in order to regulate theflow of electrical energy between the energy store and the electricalmachine. The electrical machine can in this way alternate betweenworking as an engine and as a generator, depending on the operatingcondition of the vehicle. When the vehicle is braked, the electricalmachine generates electrical energy, which is stored in the energystore. This is generally known as “regenerative braking”, and it leadsto the vehicle being braked with the aid of the electrical machine andthe combustion engine. The electrical energy that is stored is laterused for the operation of the vehicle.

An epicyclic gear normally comprises three components that are arrangedin a manner that allows rotation relative to each other. Thesecomponents are a sun gear, a planet wheel carrier and a ring gear.Knowledge of the numbers of teeth on the sun gear and ring gear allowsthe mutual rates of revolution of the three components to be determinedduring operation. One of the components of the epicyclic gear may beconnected to an output shaft of a combustion engine. Thus this componentof the epicyclic gear rotates with a rate of revolution that correspondsto the rate of revolution of the output shaft of the combustion engine.A second component of the epicyclic gear may be connected to an inputshaft to a gearbox. Thus this component of the epicyclic gear rotateswith the same rate of revolution as the input shaft to the gearbox. Athird component of the epicyclic gear is connected to a rotor of anelectrical machine, in order to achieve hybrid operation. Thus thiscomponent of the epicyclic gear rotates with the same rate of revolutionas the rotor of the electrical machine, if they are directly connectedto each other. Alternatively, the electrical machine may be connected tothe third component of the epicyclic gear through a transmission thathas a gear exchange. In this case, the electrical machine and the thirdcomponent of the epicyclic gear may rotate with different rates ofrevolution. At least one of the rate of revolution and the torquedeveloped by electrical machines may be regulated in steplessincrements. During operation, when the input shaft to the gearbox is tobe given at least one of a desired rate of revolution and torque, acontrol unit calculates, given knowledge of the rate of revolution ofthe combustion engine, the rate of revolution with which the thirdcomponent must be driven in order for the input shaft to the gearbox tobe given the desired rate of revolution. A control unit activates theelectrical machine such that it gives the calculated rate of revolutionto the third component, and thus gives the desired rate of revolution tothe input shaft to the gearbox.

By connecting together the output shaft of the combustion engine, therotor of the electrical machine and the input shaft to the gearbox usingan epicyclic gear, the conventional clutch mechanism can be avoided.During acceleration of the vehicle, increased torque is to be suppliedfrom the combustion engine and the electrical machine to the gearbox andonwards to the driving wheels of the vehicle. Since both the combustionengine and the electrical machine are connected to the epicyclic gear,the greatest possible torque that can be supplied by the combustionengine and electrical machine will be limited by any one of these driveunits, the greatest torque of which is lower than the greatest torque ofthe second drive unit, having taken the gear exchange between them intoconsideration. In the case in which the greatest torque of theelectrical machine is lower than the greatest torque of the combustionengine, having taken the gear exchange between them into account, theelectrical machine will not be able to produce a sufficiently largereactive torque to the epicyclic gear, and this leads to the combustionengine not being able to transfer its highest torque to the gearbox andonwards to the driving wheels of the vehicle. The highest torque thatcan be transferred to the gearbox is in this way limited by the power ofthe electrical machine. This is made clear also by the equation known asthe “planetary equation”.

There are disadvantages associated with using a conventional clutch thatdisconnects the input shaft to the gearbox from the combustion enginewhile gear-change processes are taking place in the gearbox, such as theheating of the lamellae of the clutch, which results in wear to theclutch lamellae and to increased fuel consumption. Furthermore, aconventional clutch mechanism is relatively heavy and expensive. Also,it occupies a relatively large space in the vehicle.

The document EP-B1-1126987 discloses a gearbox with double epicyclicgears. The sun gear of each epicyclic gear is connected to an electricalmachine, and the ring gears of the epicyclic gears are connected to eachother. The planet gear carriers of each epicyclic gear are connected toa number of gear pairs, in such a manner that an infinite number of gearsteps is obtained. Another document, EP-B 1-1280677, reveals also howthe epicyclic gears can be bridged by a gear step arranged at the outputshaft of the combustion engine.

The document US-A1-20050227803 discloses a vehicle transmission with twoelectrical machines, each one of which is connected to a sun gear in oneof two epicyclic gears. The epicyclic gears have a common planet gearcarrier, which is connected to the input shaft of the transmission.

The document WO2008/046185-A1 discloses a hybrid transmission with twoepicyclic gears, whereby an electrical machine is connected to one ofthe epicyclic gears and a double clutch interacts with the secondepicyclic gear. The two epicyclic gears interact also with each otherthrough a cogged wheel transmission.

SUMMARY OF THE INVENTION

Despite known solutions in the technical area being available, there isa need to develop further a gearbox that changes gears withoutinterruption in torque, that demonstrates a regenerative brakearrangement, that has a compact design, that has a high reliability andhigh dependability, that demonstrates low weight, and that under certainoperating conditions is self-sufficient with respect to the supply ofelectricity.

The space available for the drive arrangement in a vehicle is oftenlimited. If the drive arrangement comprises several components, such asa combustion engine, an electrical machine, a gearbox and an epicyclicgear, the design must be compact. If further components, such as aregenerative brake arrangement, are to be included, there will be evenstricter demands for compact components that are parts of the drivearrangement. At the same time, the components that are parts of thedrive arrangement must be designed with dimensions that can absorb thenecessary forces and torques.

A large number of gear steps are required in certain types of vehicle,in particular in lorries and buses. In this case, the number ofcomponents that are parts of the gearbox increases, and the gearbox alsomust be dimensioned to absorb large forces and torques that arise insuch heavy vehicles. This results in the size and weight of the gearboxincreasing.

High demands are placed also on high reliability and high dependabilityfor the components that are parts of the drive arrangement. Wear arisesin cases in which the gearbox contains lamellar clutches, which wearinfluences the reliability and lifetime of the gearbox.

Kinetic energy is converted into electrical energy during regenerativebraking, which electrical energy is stored in an energy store, such asaccumulators. One factor that influences the lifetime of the energystore is the number of cycles that the energy store supplies current tothe electrical machines and receives current from them. The greater thenumber of cycles, the shorter will be the lifetime of the energy store.

The purpose of the present invention is to provide a gearbox thatchanges gear without interruption in torque.

A further purpose of the invention is to provide a gearbox with aregenerative brake arrangement.

A further purpose of the invention is to provide a gearbox for avehicle, which gearbox can be connected directly to an output shaft atthe gearbox.

A further purpose of the present invention is to provide a gearbox thathas a compact design.

A further purpose of the present invention is to provide a gearbox thathas high reliability and high dependability.

A further purpose of the invention is to provide a gearbox for avehicle, which gearbox demonstrates low weight.

A further purpose of the present invention is to provide a gearbox thatis self-sufficient with respect to electricity under certain operatingconditions.

A further purpose of the present invention is to provide a gearbox witha regenerative brake arrangement that increases the lifetime of anenergy store connected to the regenerative brake arrangement.

A further purpose of the invention is to provide a new and advantageouscomputer program for the control of the gearbox.

A further purpose of the present invention is to provide a gearbox in ahybrid propulsion line, which gearbox can be controlled without theinfluence of a combustion engine.

These purposes are achieved with the gearbox specified in theintroduction.

These purposes are achieved with the vehicle specified in theintroduction.

These purposes are achieved also with the method for controlling thegearbox that is specified in the introduction.

These purposes are achieved also with the computer program forcontrolling the gearbox that is specified in the introduction.

These purposes are achieved also with the computer program product forcontrolling the gearbox that is specified in the introduction.

By providing the gearbox, which comprises two epicyclic gears connectedto each other, with a gear element that is arranged at the side shaft ina manner that allows it to be disengaged, a number of gear steps areobtained, where torque from one of the epicyclic gears can betransferred to the side shaft and onwards from the side shaft to a mainshaft that is connected to the other epicyclic gear in order finally totransfer the torque to the output shaft of the gearbox.

The electrical machines that are connected to the epicyclic gears caneither generate current or supply torque, or both generate current andsupply torque, depending in the desired operating condition. Theelectrical machines can also provide each other with current in certainoperating conditions.

According to one embodiment, a first planet gear carrier at the firstepicyclic gear is connected to a second sun gear at the second epicyclicgear, a first sun gear at the first epicyclic gear is connected to thefirst main shaft and a second planet gear carrier at the secondepicyclic gear is connected to the second main shaft. A transmissionthat changes gear without interruption in torque is in this wayachieved.

According to a further embodiment of the invention, the gearbox isprovided with a number of gear pairs that comprise a cogged wheel thatcan be mechanically locked with a side shaft. In this way a number offixed gear steps are obtained, between which it is possible to changegears without interruption in torque. The cogged wheels that can beengaged on the side shaft mean also that a compact design with highreliability and high dependability is obtained.

With the gearbox according to the invention, conventional slip clutchesbetween the combustion engine and the gearbox can be avoided.

According to one embodiment, a lock mechanism is arranged to connect ina fixed manner the output shaft of the combustion engine with thegearbox housing. In this way, also the first planet gear carrier will belocked fixed to the gearbox housing. By locking the output shaft of thecombustion engine and the planet gear carrier to the gearbox housing bymeans of the lock mechanism, the gearbox, and thus also the vehicle,will become adapted for electrical operation by the electrical machines.Thus the electrical machines provide a torque to the output shaft of thegearbox.

According to one embodiment, first and second coupling units arearranged between the planet gear carrier and the sun gear of the firstand second epicyclic gears, respectively. It is the task of the couplingunits to lock the relevant planet gear carrier to the sun gear. When theplanet gear carrier and the sun gear are connected to each other, theforce from the combustion engine will pass through the planet gearcarrier, the coupling unit, the sun gear and onwards to the gearbox,which results in the planet gears not absorbing any torque. This meansthat the dimensions of the planet gears can be adapted solely to thetorque of the electrical machine instead of to the torque of thecombustion engine, which in turn means that the planet gears can bedesigned with smaller dimensions. Thus, a drive arrangement according tothe invention that has a compact design, low weight and low cost ofmanufacture is in this way obtained.

It is preferable that the coupling units and lock mechanisms comprise aring-shaped sheath that is displaced axially between its engaged anddisengaged positions. The sheath essentially concentrically surroundsthe rotating components of the gearbox and it is displaced between theengaged and disengaged positions by means of a force element. A compactdesign with low weight and low cost of manufacture is in this wayobtained.

The gearbox may be preferably provided with a number of gear pairs thatcomprise cogged wheels that can be mechanically engaged and disengagedwith a side shaft. In this way a number of fixed gear steps areobtained, between which it is possible to change gears withoutinterruption in torque. The cogged wheels that can be engaged on theside shaft mean also that a compact design with high reliability andhigh dependability is obtained. Alternatively, cogged wheel drives canbe arranged at the gear pairs, such that they can be engaged anddisengaged at least one of the first and second main shafts.

Each one of the gear pairs has a gear exchange that is adapted to thedesired driving performance of the vehicle. It is appropriate that thegear pair with the highest gear exchange, relative to the other gearpairs, is engaged when the lowest gear has been selected.

In order to disengage the sun gear and planet gear carrier at therelevant epicyclic gear, at least one of the first and second electricalmachines is controlled such that torque balance is prevalent in theepicyclic gear. When torque balance has been achieved, the first or thesecond coupling unit is displaced such that the sun gear and the planetgear carrier are no longer mechanically connected to each other.

The term “torque balance” is here used to denote a condition in which atorque acts on a ring gear arranged at the epicyclic gear, correspondingto the product of the torque that acts on the planet gear carrier of theepicyclic gear and the gear exchange ratio of the planet gear, while atthe same time a torque acts on the sun gear of the epicyclic gear,corresponding to the product of the torque that acts on the planet gearcarrier and the gear exchange ratio of the planet gear. In the case inwhich two of the component parts of the epicyclic gear, sun gear, ringgear and planet gear carrier, are connected by means of a coupling unit,this coupling unit transfers no torque between the components of theepicyclic gear when torque balance is prevalent. The coupling unit canin this way be displaced in a simple manner, and the components of theepicyclic gear disengaged.

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the invention will be described as an examplebelow with reference to attached drawings, of which:

FIG. 1 shows schematically a vehicle in a side view with a gearboxaccording to the present invention,

FIG. 2 shows a schematic side view of the gearbox according to thepresent invention,

FIG. 3 shows a schematic view of the gearbox according to presentinvention, and

FIG. 4 shows a flow diagram concerning a method to control the gearboxaccording to the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 shows schematically a side view of a vehicle 1 that comprises agearbox 2 according to the present invention. A combustion engine 4 isconnected to the gearbox 2 and the gearbox 2 is further connected to thedriving wheels 6 of the vehicle 1.

FIG. 2 shows a schematic side view of the gearbox 2 according to thepresent invention. The gearbox 2 comprises an input shaft 8, first andsecond epicyclic gears 10 and 12, first and second electrical machines14 and 16, a side shaft 18 and an output shaft 20. The first epicyclicgear 10 has a first ring gear 22, to which a first rotor 24 at the firstelectrical machine 14 is connected. The first epicyclic gear 10 has alsoa first sun gear 26. The second epicyclic gear 12 has a second ring gear28, to which a second rotor 30 at the second electrical machine 16 isconnected. The second epicyclic gear 12 has a second sun gear 32. Thefirst and second sun gears 26 and 32 are arranged coaxially, which,according to the design that is shown, results in a first main shaft 34arranged at the first sun gear 26 that extends inside a second mainshaft 36 arranged at the second sun gear 32, which second main shaft 36is provided with a central bore 38. It is possible also to arrange thefirst main shaft 34 parallel to and at the side of the second main shaft36.

The first electrical machine 14 is provided with a first stator 40 thatis connected to the vehicle 1, through a gear housing 42 that surroundsthe gearbox 2. The second electrical machine 16 is provided with asecond stator 44 that is connected to the vehicle 1, through the gearhousing 42 that surrounds the gearbox 2. The first electrical machine 14and second electrical machine 16 are connected to an energy store 46,such as a battery, that drives the electrical machines 14 and 16depending on the operating condition of the vehicle 1. In otheroperating conditions, the electrical machines 14 and 16 can function asgenerators, whereby current is supplied to the energy store 46. Anelectronic control unit 48 is connected to the energy store 46 andcontrols the supply of current to the electrical machines 14 and 16. Itis preferable that the energy store 46 be connected to the electricalmachines 14 and 16 through a switch 49 that is connected to the controlunit 48. In certain operating conditions, the electrical machines 14 and16 can also drive each other. Electrical energy is then led from oneelectrical machine 14, 16 to the other electrical machine 14, 16 throughthe switch 49 that is connected to the electrical machines 14, 16. It ispossible in this way to achieve a power balance between the electricalmachines 14, 16. Another computer 53 may be connected to the controlunit 48 and to the gearbox 2. By leading electrical energy from one ofthe electrical machines 14, 16 to the other electrical machine 14, 16through the switch 49, electrical energy will not be led to and from theenergy store 46. In this way, the conditions required for an increasedlifetime of the energy store 46 are achieved. It is thus possible alsoto carry out gear changes and to propel the vehicle 1 without an energystore 46.

The first epicyclic gear 10 is provided with a first planet gear carrier50, on which a first set of planet gears 52 is mounted in bearings. Thesecond epicyclic gear 12 is provided with a second planet gear carrier51, on which a second set of planet gears 54 is mounted in bearings. Thefirst set of planet gears 52 interacts with the first ring gear 22 andwith the first sun gear 26. The second set of planet gears 54 interactswith the second ring gear 28 and the second sun gear 32. The input shaft8 of the gearbox 2 is connected to the first planet gear carrier 50. Thefirst planet gear carrier 50 at the first epicyclic gear 10 is directlyand fixed connected to the second sun gear 32 at the second epicyclicgear 12. The first planet gear carrier 50 and the second sun gear 32 inthis way will always demonstrate the same direction of rotation and thesame rate of revolution.

A first coupling unit 56 is arranged between the first sun gear 26 andthe first planet gear carrier 50. By arranging the first coupling unit56 such that the first sun gear 26 and the first planet gear carrier 50are connected to each other and thus not able to rotate relative to eachother, the first planet gear carrier 50 and the first sun gear 26 willrotate with equal rates of revolution.

A second coupling unit 58 is arranged between the second sun gear 32 andthe second planet gear carrier 51. By arranging the second coupling unit58 such that the second sun gear 32 and the second planet gear carrier51 are connected to each other and thus not able to rotate relative toeach other, the second planet gear carrier 51 and the second sun gear 32will rotate with equal rates of revolution.

It is preferable that the first and second coupling units 56, 58comprise first and second coupling sheaths 55 and 57 equipped withsplines that can be displaced axially at a spline-equipped section withthe first and second planet gear carrier 50 and 51 and at aspline-equipped section with the relevant sun gear 26 and 32. Bydisplacing the relevant coupling sheath 55, 57 such that thespline-equipped sections are connected through the relevant couplingsheath 55, 57, the first planet gear carrier 50 and the first sun gear26, and the second planet gear carrier 51 and the second sun gear 32,will become mutually locked to each other, and will not be able torotate relative to each other.

The first and the second coupling units 56, 58 according to the designshown in FIG. 2 are arranged between the first sun gear 26 and the firstplanet gear carrier 50 and between the second sun gear 32 and the secondplanet gear carrier 51, respectively. It is, however, possible toarrange a further or an alternative coupling unit (not shown in thedrawings) between the first ring gear 22 and the first planet gearcarrier 50, and also to arrange a further or alternative coupling unit(not shown in the drawings) between the second ring gear 28 and thesecond planet gear carrier 51.

A third coupling unit 59 is arranged in this embodiment between thefirst ring gear 22 and the gear housing 42. By arranging the thirdcoupling unit 59 such that the first ring gear 22 and the gear housing42 are connected to each other and thus not able to rotate relative toeach other, a gearing down of torque will take place, i.e. a gearing upof the rate of revolution from the planet gear carrier 50 to the firstsun gear 26 will take place.

A fourth coupling unit 61 is arranged in this embodiment between thesecond ring gear 28 and the gear housing 42. By arranging the fourthcoupling unit 61 such that the second ring gear 28 and the gear housing42 are connected to each other and thus not able to rotate relative toeach other, a gearing down of torque will take place, i.e. a gearing upof the rate of revolution from the planet gear carrier 50 to the secondsun gear 32 will take place.

It is preferable that the third and fourth coupling units 59, 61comprise a third and fourth coupling sheath 65 and 67 equipped withsplines that can be displaced axially at a spline-equipped section withthe first and second ring gears 22 and 28 and at a spline-equippedsection with the gear housing 42. By displacing the relevant couplingsheath 65, 67 such that the spline-equipped sections are connectedthrough the relevant coupling sheath 65, 67, the first ring gear 22 andthe gear housing 42, and the second ring gear 28 and the gear housing42, will become mutually locked to each other, and will not be able torotate relative to each other.

A transmission arrangement 19 is connected to the first and second mainshaft 34, 36, which transmission arrangement comprises a first gear pair60 that is arranged between the first epicyclic gear 10 and the outputshaft 20. The first gear pair 60 comprises a first cogged wheel drive 62and a first cogged wheel 64, which interact with each other. A secondgear pair 66 is arranged between the second epicyclic gear 12 and theoutput shaft 20. The second gear pair 66 comprises a second cogged wheeldrive 68 and a second cogged wheel 70, which interact with each other. Athird gear pair 72 is arranged between the first epicyclic gear 10 andthe output shaft 20. The third gear pair 72 comprises a third coggedwheel drive 74 and a third cogged wheel 76, which interact with eachother. A fourth gear pair 78 is arranged between the second epicyclicgear 12 and the output shaft 20. The fourth gear pair 78 comprises afourth cogged wheel drive 80 and a fourth cogged wheel 82, whichinteract with each other.

The first and third cogged wheel drives 62 and 74 are arranged at thefirst main shaft 34. The first and third cogged wheel drives 62 and 74are fixed connected to the first main shaft 34, such that they cannotrotate relative to the first main shaft 34. The second and fourth coggedwheel drives 68 and 80 are arranged at the second main shaft 36. Thesecond and fourth cogged wheel drive 68 and 80 are fixed connected tothe second main shaft 36, such that they cannot rotate relative to thesecond main shaft 36.

The side shaft 18 extends essentially parallel to the first and secondmain shafts 34 and 36. The first, second, third and fourth cogged wheels64, 70, 76 and 82 are arranged in bearings at the side shaft 18. Thefirst cogged wheel drive 62 interacts with the first cogged wheel 64,the second cogged wheel drive 68 interacts with the second cogged wheel70, the third cogged wheel drive 74 interacts with the third coggedwheel 76 and the fourth cogged wheel drive 80 interacts with the fourthcogged wheel 82.

The first, second, third and fourth cogged wheels 64, 70, 76 and 82 canbe individually locked engaged and disengaged at the side shaft 18 withthe aid of first, second, third and fourth coupling elements 84, 86, 88and 90. The coupling elements 84, 86, 88 and 90 are preferablyconstituted by sections equipped with splines designed at the coggedwheels 64, 70, 76 and 82 and the side shaft 18 that interact with thefifth and sixth coupling sheaths 83, 85, which interact mechanicallywith the sections equipped with splines at the first to fourth coggedwheels 64, 70, 76 and 82, respectively, and the side shaft 18. It ispreferable that the first and third coupling elements 84, 88 areprovided with a common coupling sheath 83, and it is preferable that thesecond and fourth coupling elements 86, 90 are provided with a commoncoupling sheath 85. When in the disengaged condition, a relativerotation can arise between the cogged wheels 64, 70, 76 and 82 and theside shaft 18. The coupling elements 84, 86, 88 and 90 may beconstituted also by friction couplings. Also a fifth cogged wheel 92 isarranged at the side shaft 18 that interacts with a sixth cogged wheel94, which is arranged at the output shaft 20 of the gearbox 2.

The side shaft 18 is arranged between the relevant first or secondepicyclic gear 10, 12 and the output shaft 20, such that side shaft 18is connected to the output shaft 20 through a final gear or a fifth gearpair 21, that comprises the fifth and sixth cogged wheels 92, 94. Thefifth cogged wheel 92 is arranged at the side shaft 18 by means of afifth coupling element 93, in a manner that allows it to be engaged anddisengaged.

By disengaging the fifth cogged wheel 92 that is arranged at the sideshaft 18 in a manner that allows it to be disengaged, it will becomepossible to transfer torque from the second epicyclic gear 12 to theside shaft 18 through the second gear pair 66 and to transfer torqueonwards from the side shaft 18 to the output shaft 20 through the firstgear pair 60. In this way, a number of gear steps are obtained, wheretorque from one of the epicyclic gears 10, 12 can be transferred to theside shaft 18 and onwards from the side shaft 18 to a main shaft 34, 36that is connected to the other epicyclic gear 10, 12, in order finallyto transfer torque to the output shaft 20 of the gearbox 2. Thisrequires, however, that a coupling mechanism 96 arranged between thefirst main shaft 34 and the output shaft 20 is engaged, which will bedescribed in more detail below.

The fifth cogged wheel 92 can be locked and freed at the side shaft 18with the aid of a fifth coupling element 93. It is preferable that thecoupling element 93 by constituted by sections that are equipped withsplines designed at the fifth cogged wheel 92 and the side shaft 18,which sections interact with a ninth coupling sheath 87 that interactsmechanically with the sections that are equipped with splines at thefifth cogged wheel 92 and the side shaft 18. When in the disengagedcondition, a relative rotation can arise between the fifth cogged wheel92 and the side shaft 18. The fifth coupling element 93 may beconstituted also by friction couplings.

During a number of gear change operations when the ring gears of theepicyclic gears 10, 12 are locked fixed at the gear housing 42 with theaid of the third and fourth coupling units 59, 61 the torque will begeared down after the first epicyclic gear 10 and geared up after thesecond epicyclic gear 12. When the transfer of torque over the firstmain shaft 34 through the side shaft 18 becomes less after the firstepicyclic gear 10, shafts, cogged drives and cogged wheels that areconnected to it can be given smaller dimensions, which will make thegearbox 2 more compact. Also a large number of gear steps can beobtained without it being necessary to arrange a number of further gearpairs in the gearbox 2. In this way, also the weight and cost of thegearbox 2 are reduced. The fifth and sixth cogged wheels 92 and 94 willfunction as a fifth gear pair 21 that transfers torque to the outputshaft 20 of the gearbox 2.

The transfer of torque from the input shaft 8 of the gearbox 2 to theoutput shaft 20 of the gearbox 2 takes place through either the first 10or the second epicyclic gear 12 and the side shaft 18. The transfer oftorque may take place also directly through the first epicyclic gear 10,the first sun gear 26 of which is connected through the first main shaft34 to the output shaft 20 of the gearbox 2 through a coupling mechanism96. It is preferable that the coupling mechanism 96 comprise a seventhcoupling sheath 100 equipped with splines, which coupling sheath can beaxially displaced at the first main shaft 34 and the sections of theoutput axel 20 that are equipped with splines. By displacing the seventhcoupling sheath 100 such that the sections that are equipped withsplines are connected through the seventh coupling sheath 100, the firstmain shaft 34 will become fixed locked with the output shaft 20, andthey will thus demonstrate on rotation the same rate of revolution. Bydisengaging the fifth cogged wheel 92 of the fifth gear pair 21 from theside shaft 18, torque from the second epicyclic gear 12 can betransferred to the side shaft 18 and onwards from the side shaft 18 tothe main shaft 34, which is connected to the first epicyclic gear 10, inorder finally to transfer torque to the output shaft 20 of the gearbox 2through the coupling mechanism 96.

During operation, the gearbox 2 may work in certain operating conditionssuch that one of the sun gears 26 or 32 is locked against the first orsecond planet gear carrier 50 or 51 with the aid of the first or secondcoupling unit 56 or 58. The first or second main shaft 34 or 36 willthen be given the same rate of revolution as the input shaft 8 of thegearbox 2, depending on which sun gear 26 or 32 that has been lockedfixed at the relevant planet gear carrier 50 or 51. One or both of theelectrical machines 14 and 16 may function as a generator in order togenerate electrical energy to the energy store 46. Alternatively, theelectrical machine 14 or 16 may provide an increase in torque in orderin this way to increase the torque at the output shaft 20. Theelectrical machines 14 and 16 will, under certain operating conditions,provide each other with electrical energy, independently of the energystore 46.

Also the gearbox 2 may, in certain operating conditions, function suchthat one of the rotors 24 and 30 at the electrical machines 14 and 16 islocked fixed with the gear housing 42 through the ring gears 22 and 28,while the second electrical machine 14 and 16 functions as a generatorin order to generate electrical energy to the energy store 46, whichwill be explained in more detail below. The electrical machine 14 or 16whose rotor 24 or 30 is locked fixed with the gear housing 42 absorbs areactive torque from the ring gear 22 or 28, before the locking iscarried out with the aid of the third or fourth coupling unit 59 or 61.Instead of functioning as a generator, the electrical machine 14 or 16may provide an increase in torque in order in this way to increase thetorque at the output shaft 20.

It is possible also that both the first and second electrical machines14 and 16 generate current to the energy store 46 at the same time. Thedriver releases the accelerator pedal (not shown in the drawings) of thevehicle 1 during engine braking. The output shaft 20 of the gearbox 2then drives either one or both of the electrical machines 14 and 16,while the combustion engine 4 and the electrical machines 14 and 16engine provide at the same time engine braking. The electrical machines14 and 16 generate in this case electrical energy that is stored in theenergy store 46 in the vehicle 1. This operating condition is known as“regenerative braking”. In order to make a more powerful braking effectpossible, the output shaft 97 of the combustion engine 4 may be fixedlocked and in this way prevented from rotating. Thus, only one or bothof the electrical machines 14 and 16 will function as a brake andgenerate electrical energy, which is stored in the energy store 46. Thelocking of the output shaft 97 of the combustion engine 4 may be carriedout also when the vehicle is to be accelerated by only one or both ofthe electrical machines 14 and 16. If the torque of one or both of theelectrical machines 14 and 16 exceeds the torque of the combustionengine 4, taking the gear exchange between them into consideration, thecombustion engine 4 will not be able to withstand the large torque thatthe electrical machines 14 and 16 produce, for which reason it will benecessary to lock fixed the output shaft 97 of the combustion engine 4.The locking of the output shaft 97 of the combustion engine 4 ispreferably carried out with a lock arrangement 102 that is arrangedbetween the first planet gear carrier 50 and the gear housing 42. Bylocking the first planet gear carrier 50 and the gear housing 42, alsothe output shaft 97 of the combustion engine 4 will be locked, since theoutput shaft 97 of the combustion engine 4 is connected to the firstplanet gear carrier 50 through the input shaft 8 of the gearbox 2. It ispreferable that the lock arrangement 102 comprise an eighth couplingsheath 104 equipped with splines that can be displaced axially at aspline-equipped section with the first planet gear carrier 50 and at aspline-equipped section with the gear housing 42. By displacing theeighth coupling sheath 104 such that the sections that are equipped withsplines are connected through the coupling sheath 104, the first planetgear carrier 50 and thus also the output shaft 97 of the combustionengine 4 will be prevented from rotating.

The control unit 48 is connected to the electrical machines 14 and 16and is adapted to control the electrical machines 14 and 16 such thatunder certain suitable operating conditions they use stored electricalenergy in order to provide driving force to the output shaft 20 of thegearbox 2, and such that under other operating conditions they use thekinetic energy of the output shaft 20 of the gearbox 2 in order toproduce and store electrical energy. The control unit 48 thus detects atleast one of the rate of revolution and the torque at the output shaft97 of the combustion engine 4 through sensors 98 arranged at theelectrical machines 14 and 16 and at the output shaft 20 of the gearbox2 in order in this way to collect information and to control theelectrical machines 14 and 16 such that they function as electric motorsor generators. The control unit 48 may be a computer with appropriatesoftware for this purpose. The control unit 48 controls also the flow ofelectrical energy between the energy store 46 and the relevant stator 40and 44 at the electrical machines 14 and 16. In conditions in which theelectrical machines 14 and 16 function as motors, stored electricalenergy is supplied from the energy store 46 to the relevant stator 40and 44. In conditions in which the electrical machines 14 and 16function as generators, electrical energy is supplied from the relevantstator 40 and 44 to the energy store 46. The electrical machines 14 and16 can, however, as has been mentioned above, provide each other withelectrical energy under certain operating conditions, independently ofthe energy store 46.

The first, second, third and fourth coupling units 56, 58, 59 and 61,the first, second, third, fourth and fifth coupling elements 84, 86, 88,90 and 93, the coupling mechanism 96 between the first main shaft 34 andthe output shaft 20, and the lock arrangement 102 between the firstplanet gear carrier 50 and the gear housing 42 are connected to thecontrol unit 48 through the relevant coupling sheaths. It is preferablethat these components are activated and deactivated by electricalsignals from the control unit 48. It is preferable that the couplingsheaths are displaced by force providers, not shown in the drawings,such as hydraulically or pneumatically powered cylinders. It is possibleto displace the coupling sheaths also by electrically powered forceproviders.

According to the embodiment in FIG. 2, four cogged wheel drives 62, 68,74 and 80 and four cogged wheels 64, 70, 76 and 82 are shown togetherwith two epicyclic gears 10 and 12 with their associated electricalmachines 14 and 16. It is, however, possible to design the gearbox 2with a greater or lesser number of cogged wheel drives and cogged wheelsand with a greater number of epicyclic gears with their associatedelectrical machines.

According to FIG. 3, there is illustrated a hybrid propulsion line 3according to FIG. 2 in a simplified schematic view in which certaincomponents have been omitted for reasons of clarity. FIG. 3 shows a gearpair G1 connected to the first main shaft 34 and thus also to the firstepicyclic gear 10, and a gear pair G2 connected to the second main shaft36 and thus also to the second epicyclic gear 12. These gear pairs G1,G2 are connected also to the output shaft 20 through the side shaft 18.The gear pair G1 that is connected to the first main shaft 34 may beconstituted by, for example, the first gear pair 60 or the third gearpair 72 as described in FIGS. 2 and 3, and it may comprise also furthergear pairs. The gear pair G2 that is connected to the second main shaft36 may be constituted by, for example, the second gear pair 66 or thefourth gear pair 78 as described in FIGS. 2 and 3, and it may comprisealso further gear pairs. Furthermore, the fifth gear pair G3, 21 that isconnected to the output shaft 20 and the side shaft 18 and that isdescribed also in FIGS. 2 and 3 is shown. G3 may, however, beconstituted by further gear pairs. When changing gear, a suitable gearpair from the relevant group G1, G2, G3 is selected.

At least one, gear pair G1, 60, 72 that is connected to the firstepicyclic gear 10 comprises at least one cogged wheel drive 62, 74 andcogged wheel 64, 76 arranged to interact with each other, which coggedwheel drive 62, 74 may be arranged such that it can be engaged anddisengaged at the first main shaft 34 arranged with the first epicyclicgear 10. At least one cogged wheel 64, 76 may be arranged such that itcan be engaged and disengaged at the side shaft 18.

At least one gear pair G2, 66, 78 that is connected to the secondepicyclic gear 12 comprises at least one cogged wheel drive 68, 80 andcogged wheel 70, 82 arranged to interact with each other, which coggedwheel drive 68, 80 may be arranged such that it can be engaged anddisengaged at the second main shaft 36 arranged with the secondepicyclic gear 12. At least one cogged wheel 70, 82 may be arranged suchthat it can be engaged and disengaged at the side shaft 18.

Gearing up from the first to the highest gear when the gearbox 2 isarranged in a vehicle 1 will be described below. The input shaft 8 ofthe gearbox 2 is connected to the output shaft 97 of the combustionengine 4 of the vehicle 1. The output shaft 20 of the gearbox 2 isconnected to a drive shaft 99 at the vehicle 1. During idling of thecombustion engine 4 and when the vehicle 1 is stationary, the inputshaft 8 of the gearbox 2 rotates while the output shaft 20 of thegearbox 2 is at the same time stationary. The lock arrangement 102 isdeactivated such that the output shaft 97 of the combustion engine 4 canrotate freely. Since the input shaft 8 of the gearbox 2 rotates, alsothe first planet gear carrier 50 will rotate, which leads to the firstset of planet gears 52 rotating. Since the first planet gear carrier 50is connected to the second sun gear 32, the second sun gear 32 and thusalso the second set of planet gears 54 will rotate. By not supplyingcurrent and not withdrawing current from the first and second electricalmachines 14 and 16, the first and second ring gears 22 and 28, which areconnected to the first and second rotors 24 and 30, respectively, at therelevant electrical machine 14 and 16, will rotate freely, whereby notorque is absorbed by the ring gears 22 and 28. The first, second, thirdand fourth coupling units 56, 58, 59 and 61 are disengaged and thus arenot engaged. Thus, no torque will be transferred from the combustionengine 4 to the sun gears 26 and 32 of the epicyclic gears 10 and 12.The coupling mechanism 96 between the first main shaft 34 and the outputshaft 20 is disengaged, such that the first main shaft 34 and the outputshaft 20 can rotate freely relative to each other. Since the sun gears26 and 32 and the output shaft 20 of the gearbox 2 are in this phasestationary, also the side shaft 18 is stationary. In a first step thefourth cogged wheel 82 and the third cogged wheel 76 are connected tothe side shaft 18 with the aid of the fourth and third coupling elements90 and 88. The first cogged wheel 64 and the second cogged wheel 70 aredisengaged from the side shaft 18. In this way, the first cogged wheel64 and the second cogged wheel 70 are allowed to rotate freely relativeto the side shaft 18. The fifth cogged wheel 92 at the fifth gear pair21 is locked fixed at the side shaft 18 with the aid of the fifthcoupling element 93.

In order to start rotation of the output shaft 20 of the gearbox 2 withthe purpose of driving the vehicle 1, the fourth cogged wheel drive 80and the fourth cogged wheel 82 at the side shaft 18 are to be caused torotate. This is achieved through the second planet gear carrier 51 beingcaused to rotate. When the second planet gear carrier 51 rotates, alsothe second main shaft 36 will rotate and thus also the fourth coggedwheel drive 80, which is arranged at the second main shaft 36, willrotate. The second planet gear carrier 51 is caused to rotate throughthe second ring gear 28 being controlled with the second electricalmachine 16. By activating the second electrical machine 16 andcontrolling the combustion engine 4 to a suitable rate of revolution,the vehicle 1 will start to be displaced through the second main shaft36 starting to rotate. When the second planet gear carrier 51 and thesecond sun gear 32 achieve the same rate of revolution, the second sungear 32 is locked fixed with the second planet gear carrier 51 with theaid of the second coupling unit 58. As has been mentioned above, thesecond coupling unit 58 is preferably so designed that the second sungear 32 and the second planet gear carrier 51 interact mechanically witheach other. Alternatively, the second coupling unit 58 may be designedas a glide brake or a lamellar clutch that connects in a gentle mannerthe second sun gear 32 to the second planet gear carrier 51. When thesecond sun gear 32 is connected to the second planet gear carrier 51,the second sun gear 32 will rotate at the same rate of revolution as theoutput shaft 97 of the combustion engine 4. In this way, the torqueproduced by the combustion engine 4 will be transferred to the outputshaft 20 of the gearbox 2 through the fourth cogged wheel drive 80, thefourth cogged wheel 82 at the side shaft 18, the fifth cogged wheel 92at the side shaft 18 and the sixth cogged wheel 94 at the output shaft20 of the gearbox 2. Thus the vehicle 1 will start to be displaced anddriven forwards by the first gear.

Each one of the first, second, third and fourth gear pairs 60, 66, 72,78 has a gear exchange that is adapted to the desired drivingperformance of the vehicle 1. According to the embodiment shown in FIG.2, the fourth gear pair 78 has the highest gear exchange compared withthe first, second and third gear pairs 60, 66, 72, which means that thefourth gear pair 78 is connected when the lowest gear has been selected.The second gear pair 66 transfers, just as the fourth gear pair 78 does,torque between the second main shaft 36 and the side shaft 18, and itwould be possible instead to design this with the highest gear exchangecompared with the other gear pairs 60, 72, 78, for which reason thesecond gear pair 66 in such a design would be connected when the lowestgear has been selected.

When the side shaft 18 is caused to rotate by the fourth cogged wheel 82at the side shaft 18, also the third cogged wheel 76 at the side shaft18 will rotate. In this way, the side shaft 18 drives the third coggedwheel 76, which in turn drives the third cogged wheel drive 74 at thefirst main shaft 34. When the first main shaft 34 rotates, also thefirst sun gear 26 will rotate, which in this way, depending on the rateof revolution of the output shaft 97 of the combustion engine 4 and thusalso the rate of revolution of the first planet gear carrier 50, willcause the first ring gear 22 and the first rotor 24 at the firstelectrical machine 14 to rotate. In this case, it is possible to allowthe first electrical machine 14 to function as a generator in order tosupply current to at least one of the energy store 46 and the secondelectrical machine 16. It is possible also that the second electricalmachine 16 is driven as a generator. Alternatively, the first electricalmachine 14 can provide additional torque through the control unit 48controlling the first electrical machine 14 to provide propulsivetorque.

In order to change gear from the first gear to the second gear, the lockbetween the second sun gear 32 and the second planet gear carrier 51must be disengaged, which is achieved through at least one of the firstand the second electrical machines 14, 16 being controlled such thattorque balance is prevalent in the second epicyclic gear 12. After this,which the second coupling unit 58 is controlled such that it releasesthe second sun gear 32 and the second planet gear carrier 51 from eachother. The second planet gear carrier 51 and the second main shaft 36can rotate freely, which leads to the second sun gear 32, the secondplanet gear carrier 51 and the second main shaft 36 no longer drivingthe fourth cogged wheel drive 80, which is arranged at the second mainshaft 36. This requires that the second electrical machine 16 is notdriving the second ring gear 28. The second gear is selected through thecontrol unit 48 controlling the first electrical machine 14 such that asynchronous rate of revolution arises between the first planet gearcarrier 50 and the first sun gear 26, in order to achieve a lockingbetween the first planet gear carrier 50 and the first sun gear 26. Thisis achieved through the first coupling unit 56 being controlled suchthat the first planet gear carrier 50 and the first sun gear 26 aremechanically connected to each other. Alternatively, the first couplingunit 56 may be designed as a glide brake or a lamellar clutch thatconnects in a gentle manner the first sun gear 26 and the first planetgear carrier 50. By synchronizing the control of the combustion engine 4and of the first and second electrical machines 14 and 16, it ispossible to carry out a soft and interruption-free transition from thefirst gear to the second gear.

The first main shaft 34 is now rotating and is being driven by theoutput shaft 97 of the combustion engine 4, and the first main shaft 34is now driving the third cogged wheel drive 74. The first planet gearcarrier 50 is now driving the third cogged wheel drive 74 through thefirst sun gear 26 and the first main shaft 34. Since the third coggedwheel 76 interacts with the third cogged wheel drive 74 and is fixedconnect to the side shaft 18, the third cogged wheel 76 will drive theside shaft 18, which in turn drives the fifth cogged wheel 92 at theside shaft 18. The fifth cogged wheel 92 in turn drives the output shaft20 of the gearbox 2 through the sixth cogged wheel 94, which is arrangedat the output shaft 20 of the gearbox 2. The vehicle 1 is now beingpropelled in second gear.

When the side shaft 18 is caused to rotate by the third cogged wheel 76,also the fourth cogged wheel 82 will rotate. In this way, the side shaft18 drives the fourth cogged wheel 82, which in turn drives the fourthcogged wheel drive 80 at the second main shaft 36. When the second mainshaft 36 rotates, also the second planet gear carrier 51 will rotate,which in this way, depending on the rate of revolution of the outputshaft 97 of the combustion engine 4 and thus also the rate of revolutionof the first planet gear carrier 50, will cause the second ring gear 28and the second rotor 30 at the second electrical machine 16 to rotate.In this case, it is possible to allow the second electrical machine 16to function as a generator in order to supply current to at least one ofthe energy store 46 and the first electrical machine 14. Also the secondelectrical machine 16 can provide additional torque through the controlunit 48 controlling the second electrical machine 16 to providepropulsive torque.

In order to change gear from the second gear to the third gear, thefourth cogged wheel 82 at the side shaft 18 must be disengaged from theside shaft 18 with the fourth coupling element 90, such that the fourthcogged wheel 82 can rotate freely relative to the side shaft 18. Theside shaft 18 is subsequently connected to the second cogged wheel 70 atthe side shaft 18 through the second coupling element 86. In order toachieve connection of the side shaft 18 and the second cogged wheel 70at the side shaft 18, preferably the second electrical machine 16 iscontrolled such that a synchronous rate of revolution arises between theside shaft 18 and the second cogged wheel 70 at the side shaft 18. Asynchronous rate of revolution can be determined through the rate ofrevolution of the second rotor 30 at the second electrical machine 16being measured and through the rate of revolution of the output shaft 20being measured. In this way, the rate of revolution of the second mainshaft 36 and the rate of revolution of the side shaft 18 can bedetermined through the given gear exchange ratio. The rates ofrevolution of the relevant shafts 18 and 36 are controlled, and when asynchronous rate of revolution has arisen between the side shaft 18 andthe second cogged wheel 70, the side shaft 18 and the second coggedwheel 70 are connected with the aid of the second coupling element 86.

In order to change gear from the second gear to the third gear, the lockbetween the first sun gear 26 and the first planet gear carrier 50 mustbe disengaged, which is achieved through the first and the secondelectrical machines 14, 16 being controlled such that torque balance isprevalent in the first epicyclic gear 10, after which the first couplingunit 56 is controlled such that it releases the first sun gear 26 andthe first planet gear carrier 50 from each other. The combustion engine4 is subsequently controlled such that a synchronous rate of revolutionarises between the second sun gear 32 and the second planet gear carrier51, such that the second coupling unit 58 can be engaged, in order inthis way to connect the second sun gear 32 and the second planet gearcarrier 51 by the coupling sheath 57. By synchronizing the control ofthe combustion engine 4 and of the first and second electrical machines14 and 16, it is possible to carry out a soft and interruption-freetransition from the second gear to the third gear.

The third cogged wheel 76 is disengaged through the first electricalmachine 14 being controlled such that a condition that is free of torquearises between the side shaft 18 and the third cogged wheel 76. When acondition that is free of torque arises, the third cogged wheel 76 isdisengaged from the side shaft 18 through the third coupling element 88being controlled such that it disengages the third cogged wheel 76 fromthe side shaft 18. The first electrical machine 14 is subsequentlycontrolled such that a synchronous rate of revolution arises between theside shaft 18 and the first cogged wheel 64. When a synchronous rate ofrevolution has arisen, the first cogged wheel 64 is connected to theside shaft 18 through the first coupling element 84 being controlledsuch that it connects the first cogged wheel 64 to the side shaft 18. Asynchronous rate of revolution can be determined through the rate ofrevolution of the first rotor 24 at the first electrical machine 14being measured and through the rate of revolution of the output shaft 20being measured, after which the rates of revolution of the shafts 18, 34are controlled such that a synchronous rate of revolution arises. Inthis way, the rate of revolution of the first main shaft 34 and the rateof revolution of the side shaft 18 can be determined through the givengear exchange ratio.

The second main shaft 36 is now rotating with the same rate ofrevolution as the output shaft 97 of the combustion engine 4, and thesecond main shaft 36 is now driving the second cogged wheel drive 68through the second main shaft 36. Since the second cogged wheel 70 is ininteraction with the second cogged wheel drive 68 and is fixed connectedto the side shaft 18, the second cogged wheel 70 will drive the sideshaft 18, which in turn drives the fifth cogged wheel 92 at the sideshaft 18. The fifth cogged wheel 92 in turn drives the output shaft 20of the gearbox 2 through the sixth cogged wheel 94, which is arranged atthe output shaft 20 of the gearbox 2. The vehicle 1 is now beingpropelled in third gear.

When the side shaft 18 is caused to rotate by the second cogged wheel 70at the side shaft 18, also the first cogged wheel 64 at the side shaft18 will rotate. The side shaft 18 in this way drives the first coggedwheel 64, which in turn drives the first cogged wheel drive 62 at thefirst main shaft 34. When the first main shaft 34 rotates, also thefirst sun gear 26 will rotate, which in this way, depending on the rateof revolution of the output shaft 97 of the combustion engine 4 and thusalso the rate of revolution of the first planet gear carrier 50, willcause the first ring gear 22 and the first rotor 24 at the firstelectrical machine 14 to rotate. In this case, it is possible to allowthe first electrical machine 14 to function as a generator in order tosupply current to at least one of the energy store 46 and the secondelectrical machine 16. Alternatively, the first electrical machine 14can provide additional torque through the control unit 48 controllingthe first electrical machine 14 to provide propulsive torque.

In order to change gear from the third gear to the fourth gear, the lockbetween the second sun gear 32 and the second planet gear carrier 51must be disengaged, which is achieved through the first and the secondelectrical machines 14, 16 being controlled such that torque balance isprevalent in the second epicyclic gear 12, after which the secondcoupling unit 58 is controlled such that it releases the second sun gear32 and the second planet gear carrier 51 from each other. The first ringgear 22 is subsequently braked, and when the first ring gear 22 isstationary the third coupling unit 59 is controlled such that the firstring gear 22 is connected to and united with the gear housing 42. Bysynchronizing the control of the combustion engine 4 and of the firstand second electrical machines 14 and 16, it is possible to carry out asoft and interruption-free transition from the third gear to the fourthgear.

The first main shaft 34 is now being driven by the output shaft 97 ofthe combustion engine 4, and the first main shaft 34 is now driving thefirst cogged wheel drive 62. Since the first cogged wheel 64 interactswith the first cogged wheel drive 62 and is fixed connected to the sideshaft 18, the first cogged wheel 64 will drive the side shaft 18, whichin turn drives the fifth cogged wheel 92 at the side shaft 18. The fifthcogged wheel 92 in turn drives the output shaft 20 of the gearbox 2through the sixth cogged wheel 94, which is arranged at the output shaft20 of the gearbox 2. The vehicle 1 is now being propelled in fourthgear.

When the side shaft 18 is caused to rotate by the first cogged wheel 64,also the second cogged wheel 70 at the side shaft 18 will rotate. Inthis way, the side shaft 18 drives the second cogged wheel 70, which inturn drives the second cogged wheel drive 68 at the second main shaft36. When the second main shaft 36 rotates, also the second planet gearcarrier 51 will rotate, which in this way, depending on the rate ofrevolution of the output shaft 97 of the combustion engine 4 and thusalso the rate of revolution of the first planet gear carrier 50, willcause the second sun gear 32 and the second rotor 30 at the secondelectrical machine 16 to rotate. In this case, it is possible to allowthe second electrical machine 16 to function as a generator in order tosupply current to at least one of the energy store 46 and the firstelectrical machine 14. Alternatively, the second electrical machine 16can provide additional torque through the control unit 48 controllingthe second electrical machine 16 to provide propulsive torque.

In order to change gear from the fourth gear to the fifth gear, thefirst electrical machine 14 is controlled such that torque balancearises between the first ring gear 22 and the gear housing 42. Whentorque balance has arisen between the first ring gear 22 and the gearhousing 42, the third coupling unit 59 is controlled such that the firstring gear 22 is disengaged from the gear housing 42. Torque balancecomprises not only a torque-free condition, but also a counteractingtorque such that the fourth coupling unit 61 is to be placed into acondition in which it does not transfer torque between the second ringgear 28 and the gear housing 42. The first electrical machine 14 issubsequently controlled such that a torque-free condition arises betweenthe side shaft 18 and the first cogged wheel 64. When a torque-freecondition has arisen between the side shaft 18 and the first coggedwheel 64, the first coupling element 84 is controlled such that thefirst cogged wheel 64 is disengaged from the side shaft 18. In this way,the fourth gear has been unselected. In order to select the fifth gear,the first electrical machine 14 is controlled such that a synchronousrate of revolution arises between the first main shaft 34 and the outputshaft 20. When a synchronous rate of revolution has arisen between thefirst main shaft 34 and the output shaft 20, the coupling mechanism 96is controlled such that the first main shaft 34 and the output shaft 20are connected to and united with each other. Furthermore, the firstelectrical machine 14 is controlled such that a torque-free conditionarises between the side shaft 18 and the fifth cogged wheel 92 at thefifth gear pair 21. When a torque-free condition has arisen between theside shaft 18 and the fifth cogged wheel 92, the fifth coupling element93 is controlled such that the fifth cogged wheel 92 is disengaged fromthe side shaft 18. The first electrical machine 14 is subsequentlycontrolled such that a synchronous rate of revolution arises between theside shaft 18 and the first cogged wheel 64. When a synchronous rate ofrevolution has arisen between the side shaft 18 and the first coggedwheel 64, the coupling element 84 is controlled such that the firstcogged wheel 64 is connected to and united with the side shaft 18.Finally, the combustion engine 4 is controlled such that the second ringgear 28 is stationary relative to the gear housing 42. When the secondring gear 28 is stationary, the fourth coupling unit 61 is controlledsuch that the second ring gear 28 is connected to and locked fixed tothe gear housing 42. The vehicle 1 is now being propelled in the fifthgear.

When the fifth gear has been selected, the torque from the combustionengine 4 will pass the first and second planet gear carriers 50, 51 andwill be transferred from the second main shaft 36 through the secondgear pair 66 to the side shaft 18 and onwards through the first gearpair 60 to the first main shaft 34 in order subsequently to betransferred through the coupling mechanism 96 to the output shaft 20.

In order to change gear from the fifth gear to the sixth gear, thesecond electrical machine 16 is controlled such that torque balancearises between the second ring gear 28 and the gear housing 42. Whentorque balance has arisen between the second ring gear 28 and the gearhousing 42 the fourth coupling unit 61 is controlled such that thesecond ring gear 28 is disengaged from the gear housing 42. Thecombustion engine 4 is subsequently controlled such that a synchronousrate of revolution arises between the first sun gear 26 and the firstplanet gear carrier 50. When a synchronous rate of revolution has arisenbetween the first sun gear 26 and the first planet gear carrier 50, thefirst coupling unit 56 is controlled such that the first sun gear 26 isconnect to and united with the first planet gear carrier 50.Furthermore, the second electrical machine 16 is controlled such that atorque-free condition arises between the side shaft 18 and the firstcogged wheel 64. When a torque-free condition has arisen between theside shaft 18 and the first cogged wheel 64, the coupling element 84 iscontrolled such that the first cogged wheel 64 is disengaged from theside shaft 18. Finally, the second electrical machine 16 is controlledsuch that a synchronous rate of revolution arises between the side shaft18 and the third cogged wheel 76. When a synchronous rate of revolutionhas arisen between the side shaft 18 and the third cogged wheel 76, thecoupling element 88 is controlled such that the third cogged wheel 76 isconnected to and locked fixed with the side shaft 18. The vehicle 1 isnow being propelled in the sixth gear.

When the sixth gear has been selected, the torque from the combustionengine 4 will be transferred from the first planet gear carrier 50 tothe first sun gear 26 and onwards to the first main shaft 34 in ordersubsequently to be transferred through the coupling mechanism 96 to theoutput shaft 20.

In order to change gears from the sixth gear to the seventh gear thefirst and second electrical machines 14, 16 are controlled such thattorque balance is prevalent in the first epicyclic gear 10. When torquebalance is prevalent in the first epicyclic gear 10, the first couplingunit 56 is controlled such that the first sun gear 26 is disengaged fromthe first planet gear carrier 50. The combustion engine 4 issubsequently controlled such that a synchronous rate of revolutionarises between the second sun gear 32 and the second planet gear carrier51. When a synchronous rate of revolution has arisen between the secondsun gear 32 and the second planet gear carrier 51, the second couplingunit 58 is controlled such that the second sun gear 32 is connected toand united with the second planet gear carrier 51. The vehicle 1 is nowbeing propelled in the seventh gear.

When the seventh gear has been selected, torque from the combustionengine 4 will pass the first planet gear carrier 50 and onwards to thesecond main shaft 36. Torque is subsequently transferred from the secondmain shaft 36 through the second gear pair 66 to the side shaft 18 andonwards through the third gear pair 72 to the first main shaft 34, inorder subsequently to be transferred through the coupling mechanism 96to the output shaft 20.

According to the design described above, it is stated that the gearbox 2comprises cogged wheel drives 62, 68, 74, 80 and cogged wheels 64, 70,76, 82 arranged at the main shafts 34, 36 and the side shaft 18 in orderto transfer rates of revolution and torque. It is, however, possible touse another type of transmission, such as chain and belt transmissionsin order to transfer rates of revolution and torque in the gearbox 2.

The transmission arrangement 19 demonstrates according to the embodimentabove four gear pairs 60, 66, 72, 78. The transmission arrangement 19,however, may comprise a freely chosen number of gear pairs.

As has been described above, torque is withdrawn from the gearbox 2 fromthe output shaft 20. It is possible also to withdraw torque directlyfrom the first or the second main shaft 34, 36, or directly from theside shaft 18. Torque may be withdrawn also in parallel from two orthree of the shafts 18, 34, 36 at the same time.

It is preferable that the second electrical machine 16 is driven withelectricity generated from the first electrical machine 14 in order toreduce with the second electrical machine 16 the reactive torque fromthe second epicyclic gear 12, and in order in this way to reduce thetorque transferred at the second gear pair 66. The reactive torque fromthe first epicyclic gear 10 is increased with the first electricalmachine 14, in order to increase the torque transferred at the firstgear pair 60.

It is possible also to drive the first electrical machine 14 withelectrical energy generated from the second electrical machine 16 inorder to reduce with the first electrical machine 14 the reactive torquefrom the first epicyclic gear 10, and in order in this way to reduce thetorque transferred at the first gear pair 60. The reactive torque fromthe first epicyclic gear 10 is increased with the second electricalmachine 16, in order to increase the torque transferred at the secondgear pair 66.

FIG. 4 shows a flow diagram concerning a method to control the gearbox 2according to the invention. The method according to the invention ischaracterised by the steps:

-   a) to disengage a gear element 92 that is arranged at a side shaft    18 in a manner that allows it to be disengaged and that is connected    through a final gear 21 with the output shaft 20;-   b) to transfer torque from the second epicyclic gear 12 to the side    shaft 18 through the second gear pair 66; and-   c) to transfer torque from the side shaft 18 to the output shaft 20    through the first gear pair 60.

The method comprises also the further steps:

-   d) to drive the second electrical machine 16 with electricity    generated from the first electrical machine 14 in order to reduce    with the second electrical machine 16 the reactive torque from the    second epicyclic gear 12, and in order in this way to reduce the    torque transferred at the second gear pair 66; and-   e) to increase with the first electrical machine 14 the reactive    torque from the first epicyclic gear 10, in order to increase the    torque transferred at the first gear pair 60.

The method comprises also the further steps:

-   f) to disengage with a first coupling unit 56 a first sun gear 26    arranged at the first epicyclic gear 10 and a first planet gear    carrier 50 from each other; and-   g) to connect with a fourth coupling unit 61 a second ring gear 28    arranged at the second epicyclic gear 12 and a gear housing 42 to    each other.

According to a further step of the method, the reduction and theincrease in reactive torque at the first and second electrical machines14 and 16 are synchronized, such that the torque at the output shaft 20is constant or changes in a linear manner.

Change of gear can in this way be achieved without interruption intorque through the torque at the output shaft 20 being constant orchanging in a continuous manner, during, for example, acceleration orretardation of the vehicle 1.

The specified method thus comprises all steps of a change of gearcorresponding to all gears described in the embodiment above.

According to the invention, a computer program P that is stored in atleast one of the control unit 48 and the computer 53 and that maycomprise routines for the control of the gearbox 2 according to thepresent invention is provided.

The computer program P may comprise routines to control the gearbox inorder to disengage the fifth cogged wheel 92 that is arranged at theside shaft in a manner that allows it to be disengaged and that isconnected through a fifth gear pair 21 to the output shaft 20.

The computer program P may comprise routines to control the gearbox 2 inorder to transfer torque from the second epicyclic gear 12 to the sideshaft 18 through the second gear pair 66. The computer program P maycomprise routines to control the gearbox 2 in order to transfer torquefrom the side shaft 18 to the output shaft 20 through the first gearpair 60.

The computer program P may comprise routines to control the gearbox 2such that the first electrical machine 14 is driven with electricalenergy generated from the second electrical machine 16 in order toreduce with the first electrical machine 14 the reactive torque from thefirst epicyclic gear 10, and in order in this way to reduce the torquetransferred at the first gear pair 60.

The computer program P may comprise routines to control the gearbox 2such that the reactive torque from the second epicyclic gear 12 isincreased with the second electrical machine 16, in order to increasethe torque transferred at the second gear pair 66.

The computer program P may comprise routines to control the gearbox 2such that a first coupling unit 56 a first sun gear 26 arranged at thefirst epicyclic gear 10 and a first planet gear carrier 50 are freedfrom each other.

The computer program P may comprise routines to control the gearbox 2such that a fourth coupling unit 61 a first ring gear 28 arranged at thesecond epicyclic gear 12 and a gear housing 42 are connected with eachother.

The computer program P may comprise routines to control the gearbox 2such that the reduction and the increase in reactive torque at the firstand second electrical machines 14 and 16 are synchronized, such that thetorque at the output shaft 20 is constant or changes in a linear manner.

The computer program P may be stored in an executable form or in acompressed form in at least one of a memory M and a read/write memory R.The program code may be stored in permanent form on a medium that can beread by a computer 53.

The invention concerns also a computer program product comprising aprogram code stored on a medium that can be read by a computer, in orderto carry out the method steps described above, when the computer programis run on the control unit 48 or another computer 53 connected to thecontrol unit 48.

The specified components and distinctive features that are specifiedabove may be combined between the different specified executions withinthe framework of the invention.

The invention claimed is:
 1. A gearbox comprising an input shaft and anoutput shaft; a first epicyclic gear that is connected to the inputshaft; a second epicyclic gear that is connected to the first epicyclicgear; a first electrical machine that is connected to the firstepicyclic gear; a second electrical machine that is connected to thesecond epicyclic gear; a first gear pair that is arranged between thefirst epicyclic gear and the output shaft; a second gear pair that isarranged between the second epicyclic gear and the output shaft; asecond main shaft connected to the second epicyclic gear; a secondplanet gear carrier at the second epicyclic gear that is connected tothe second main shaft; and a side shaft arranged between the respectivefirst and second epicyclic gears and the output shaft, wherein the inputshaft is connected to the first planet gear carrier; the side shaft isconnected to the output shaft through a final gear; and the final gearcomprises a gear element that is disengagably engaged at the side shaft.2. The gearbox according to claim 1, wherein a first main shaft isconnected to the first epicyclic gear; wherein the first gear pair isarranged at the first main shaft and the side shaft; and wherein thesecond gear pair is arranged at the second main shaft and the sideshaft.
 3. The gearbox according to claim 2, wherein a first planet gearcarrier at the first epicyclic gear is connected to a second sun gear atthe second epicyclic gear; and wherein a first sun gear at the firstepicyclic gear is connected to the first main shaft.
 4. The gearboxaccording to claim 2, wherein a coupling mechanism is arranged betweenthe first main shaft and the output shaft.
 5. The gearbox according toclaim 2, wherein the first gear pair comprises a first cogged wheeldrive and a first cogged wheel that interact with each other, whichfirst cogged wheel drive is fixed arranged with the first main shaft andthe first cogged wheel being disengagably engaged to the side shaft-andwherein; the second gear pair comprises a second cogged wheel drive anda second cogged wheel that interact with each other, the second coggedwheel drive being fixed to the second main shaft and the second coggedwheel being disengagably engaged to the side shaft.
 6. The gearboxaccording to claim 5, further comprising, a third gear pair that isarranged between the first epicyclic gear and the output shaft, thethird gear pair comprising a third cogged wheel drive and a third coggedwheel that interact with each other, the third cogged wheel drive beingfixed to the first main shaft and the third cogged wheel beingdisengagably engaged at the side shaft; and a fourth gear pair that isarranged between the second epicyclic gear and the output shaft; thefourth gear pair comprising a fourth cogged wheel drive and a fourthcogged wheel that interact with each other, the fourth cogged wheeldrive being fixed to the second main shaft and the fourth cogged wheelbeing disengagably engaged at the side shaft.
 7. The gearbox accordingto claim 1, wherein the gear element is disengagabley engaged at theside shaft with a fifth coupling element.
 8. The gearbox according toclaim 1, wherein the gear element of the final gear is a fifth coggedwheel, that interacts with a sixth cogged wheel, that is fixed to theoutput shaft.
 9. The gearbox according to claim 6, wherein the first,second, third and fourth cogged wheels are disengagably engaged at theside shaft with first, second, third and fourth coupling elements. 10.The gearbox according to claim 1, wherein a first rotor at the firstelectrical machine is connected to a first ring gear at the firstepicyclic gear; and a second rotor at the second electrical machine isconnected to a second ring gear at the second epicyclic gear.
 11. Thegearbox according to claim 3, wherein a first coupling unit separablyconnects the first sun gear to the first planet gear carrier; and asecond coupling unit separably connects the second sun gear to thesecond planet gear carrier.
 12. The gearbox according to claim 11,wherein a third coupling unit separably connects the first ring gear atthe first epicyclic gear to a gear housing that surrounds the gearhousing; and a fourth coupling unit separably connects a second ringgear at the second epicyclic gear to the gear housing.
 13. A vehicle,comprising an engine, and a gearbox according to claim
 1. 14. A methodto control a gearbox, the gearbox including, an input shaft and anoutput shaft; a first epicyclic gear that is connected to the inputshaft; a second epicyclic gear that is connected to the first epicyclicgear; a first electrical machine that is connected to the firstepicyclic gear; a second electrical machine that is connected to thesecond epicyclic gear; a first gear pair that is arranged between thefirst epicyclic gear and the output shaft; and a second gear pair thatis arranged between the second epicyclic gear and the output shaft,wherein a second main shaft is connected to the second epicyclic gear, asecond planet gear carrier at the second epicyclic gear is connected tothe second main shaft, and the input shaft is connected to the firstplanet gear carrier, the method comprising: a) disengaging a gearelement that is arranged at a side shaft and that is connected through afinal gear to the output shaft; b) transferring torque from the secondepicyclic gear to the side shaft through the second gear pair; and c)transferring torque from the side shaft to the output shaft through thefirst gear pair.
 15. The method according to claim 14, furthercomprising: d) driving the second electrical machine with electricalenergy generated from the first electrical machine in order to reducewith the second electrical machine the reactive torque from the secondepicyclic gear, and to reduce the torque transferred at the second gearpair; and e) increasing with the first electrical machine the reactivetorque from the first epicyclic gear, in order to increase the torquetransferred at the first gear pair.
 16. The method according to claim15, further comprising: f) disengaging with a first coupling unit afirst sun gear arranged at the first epicyclic gear and a first planetgear carrier from each other; and g) connecting with a fourth couplingunit a second ring gear arranged at the second epicyclic gear and a gearhousing to each other.
 17. The method according to claim 14, wherein areduction and an increase in reactive torque at the first and secondelectrical machines are synchronized, such that the torque at the outputshaft is constant or changes in a continuous manner.
 18. A computerproduct comprising: a non-transitory computer readable medium andprogram code stored on the medium to carry out the method according toclaim 14, when the program code is run on an electronic control unit oranother computer connected to the electronic control unit.